问题 问答题 简答题

土壤Cd污染的主要来源有哪些?

答案

参考答案:

污染源主要是铅锌矿,以及有色金属冶炼、电镀和用镉化合物作原料或触媒的工厂。镉对土壤的污染主要有气型和水型两种。气型污染主要来自工业废气。镉随废气扩散到工厂周围并自然沉降,蓄集于工厂周围的土壤中,可使土壤中的镉浓度达到40ppm。污染范围有的可达数公里。水型污染主要是铅锌矿的选矿废水和有关工业废水排入地面水或渗入地下水引起的。

阅读理解

阅读理解。

    You may think that English dictionaries have been used for many, many centuries. In fact, an English

dictionary like the kind you use today wasn't made until the time of the Qing Dynasty. Three men did most

of the important early work on dictionaries: Samuel Johnson, Noah Webster, and James Murray. These men

spent nearly all of their lives trying to collect words for their dictionaries. For them, it wasn't only a job; it

was a wonderful journey. The largest dictionary in the world is the Oxford English Dictionary, or OED for

short. The idea for this dictionary came from an important meeting in Britain in 1857. Twenty-two years later,

Oxford University asked James Murray to be the editor of its new dictionary.

    Murray had never been to college. At the age of fourteen, he left his village school in Scotland and taught

himself while working in a bank. Later he became a great teacher. After Oxford gave him the job, Murray had

a place built in the garden behind his house to do his work. Part of it was one meter underground. In winter it

felt like a barn, he had to wear a heavy coat and put his feet in a box to keep warm. Every morning, Murray

got out of bed at five o'clock and worked several hours before breakfast. Often he would work by candle light

into the evening. Murray hoped to finish the new dictionary in ten years. But after five years, he was still

adding words for the letter A! Then others went to work with Murray, including his two daughters. He worked

on the dictionary until he was very old. Forty-four years later, in 1928, other editors finished it. It included

more than 15,000 words in twelve books. And you thought your English dictionary was big!

1. The first English dictionary like we are using today _____. [ ]

A. was edited in China in the Qing Dynasty

B. has been used for many centuries

C. was completed by James Murray

D. was made in the 20th century

2. What's the meaning of the underlined sentence? [ ]

A. The editors liked their jobs very much.

B. Making dictionaries was more than their job, it took their whole lives to complete the tasks.

C. Editing dictionaries was like taking a wonderful journey.

D. It was only a job for the editors to make dictionaries.

3. Which of the following statements about the Oxford English Dictionary is NOT true? [ ]

A. It was completed by James Murray and some other people.

B. It was decided to make such a dictionary in 1857.

C. The dictionary was completed twenty-two years after it was decided to be made.

D. It took James Murray more than 5 years to add words to letter A.

4. In the last paragraph, "barn" probably is _____. [ ]

A. a hotel to live in

B. a nice house to look at

C. a place for animals to stay in

D. a room to keep cold out

5. The main purpose of writing this passage is to _____. [ ]

A. tell us why the first English dictionary was made

B. introduce who James Murray was

C. tell us how the first English dictionary was made

D. introduce us three people - Samuel Johnson, Noah Webster, and James Murray

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